<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>盒模型的计算</title>

	<style type="text/css">
		/*div{
			width: 400px;
			height: 400px;
			border: 1px solid red;
		}*/

		div{
			width: 50px;
			height: 50px;
			border: 1px solid red;
			padding: 175px;
		}

		/*div{
			width: 0;
			height: 0;
			border: 1px solid red;
			padding: 200px;
		}*/

	</style>
</head>
<body>

	<!-- 如果想保证盒子的真实宽度，加width应该减padding  减width 应该加padding -->
	<div>
		内容
	</div>
	
</body>
</html>